There are known, in the prior art, decorative pieces intended to be added to a portable object, such as a watch or piece of jewellery, and consisting in the setting of an aesthetic element on parts of said portable object acting as support.
For this purpose, the part is made of metallic alloy and is machined so that housings appear. During this machining, gripping means taking the form of hooks are made. Generally speaking, these hooks are made integral with the material forming the object that is to say in one-piece with the object. When an aesthetic element, such as a precious stone, has to be set, the latter is placed in a housing and the gripping means are folded down so as to hold said aesthetic element in the housing. This setting method is widely used for setting precious stones in metal supports since the metal has an advantageous capacity for plastic deformation. This capacity is even more advantageous with precious metals such as gold, since these precious metals are ductile and can easily be shaped. Cold plastic deformation of crystalline metals is made possible by the movements of the lattice dislocations present in the crystal lattices. The elastic limit, i.e. the stress beyond which a material starts to deform plastically, of a crystalline alloy depends on its constituent elements and on the thermomechanical history of the alloy. For conventional setting, alloys having relatively low elastic limits are generally selected to facilitate the work of the setter. In addition to a relatively low elastic limit, it is necessary for the alloy to have sufficient elongation before rupture in order to be able to fold down the gripping means without them breaking. As with the elastic limit, this elongation is the consequence both of the elements present in the alloy and of the thermomechanical history thereof. For example, gold alloys used in horology have an elastic limit on the order of 200-400 MPa and a breaking elongation of 20-40%. 1.4435 type stainless steels have an elastic limit of 200-300 MPa and a breaking elongation of 25-45%.
Nevertheless, one drawback of this method is that it is limited to supports made of ductile metals or metal alloys. Now, timepieces are increasingly made of materials with no plastic deformation, which are often hard and/or brittle, such as for example, ceramics, silicon, composites or even intermetallic alloys.
Consequently, it is no longer possible to use the current method for setting aesthetic elements, such as for example, precious stones.
This setting operation is therefore replaced by an adhesive bonding operation. Adhesive bonding has the drawback of not ensuring 100% retention of the stones since, unlike setting, this technique does not involve mechanical retention of the stones. Indeed, as the bonded areas are in most cases exposed to the external environment (humidity, sweat, UV, air pollution, . . . ) the resistance of bonding over the long term is made difficult. Consequently, retention of the stones is not ensured which is unacceptable for high quality products.